1. Technical Field
This disclosure relates to an image forming apparatus, and more specifically to an image forming apparatus for forming an image on a recording medium.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having two or more of copying, printing, scanning, facsimile, plotter, and other functions, typically form an image on a sheet serving as a recording medium according to image data by an inkjet method using ink and an electrophotographic method using toner. As the sheet is conveyed through the image forming apparatus, the sheet may curl due to a force exerted by a plurality of conveyance rollers that nips and conveys the sheet or uneven distribution of moisture contained in the sheet. For example, when the sheet is conveyed through the image forming apparatus employing the inkjet method, as an imaged side of the sheet absorbs ink, the imaged side of the sheet expands and an edge of the sheet curls toward a non-imaged side of the sheet. If the image forming apparatus includes a recording head unit incorporating a plurality of recording heads aligned in line, the recording heads eject ink onto the sheet at high speed, increasing an amount of moisture absorbed into the sheet per unit time and therefore enlarging curl of the sheet sharply. Additionally, as an amount of ink adhered to the sheet increases, an amount of curl of the sheet increases. Accordingly, the curled sheet may not be conveyed properly. For example, as the edge of the sheet is lifted, the sheet is bent upward. The bent sheet may be jammed or suffer from faulty finishing while conveyed improperly through a finisher.
In order to suppress curl of the sheet, a roller may press against the sheet while the sheet is conveyed between the conveyance rollers to bend and eliminate curl of the sheet. For example, the sheet is nipped and conveyed between a pair of rollers to eliminate curl of the sheet. However, since the pair of rollers presses against the sheet with increased pressure, ink of the image on the sheet is transferred onto one of the pair of rollers that comes into contact with the imaged side of the sheet. Thereafter, ink is retransferred from the one of the pair of rollers onto the sheet, staining the sheet. Alternatively, ink is retransferred from the one of the pair of rollers onto another one of the pair of rollers, which in turn stains the non-imaged side of the next sheet. To address this problem, a cleaner may press against and clean a roller that conveys the sheet as disclosed by JP-2011-032009-A.
However, the cleaner pressing against the roller to prevent retransfer of ink may upsize and complicate the image forming apparatus at increased manufacturing costs.